Satoshi Igarashi

A Molecular Pair of [GdNi3] Tetrahedra Bridged by Water Molecules

The authors thank the Generalitat de Catalunya for the prize ICREA Academia 2008 (G.A.) and Grant 2009SGR-1459 (E.C. and E.R.) and Spanish MCI through CTQ2009–06959 (G.A., L.B.), MAT2009-13977- C03 (M.E.), and CTQ2008–06670-C02–01 (E.C., ER). The advanced light source (S.J.T.) is supported by the U.S. Department of Energy (DE-AC02–05CH11231).

Structure-dependent spectral behavior of five-coordinate ternary copper(II) complexes containing 2,2′-dipicolylamine. X-ray crystal structures of [Cu(dpa)(pic)]ClO4, and [Cu(dpa)(pic)]PF6·H2O (dpa=2,2′dipicolylamine, pic=picolinate)

Abstract The X-ray crystal structures and the electronic absorption spectra of the two complexes in the title, [Cu(dpa)(pic)]ClO4 (1) and [Cu(dpa)(pic)]PF6·H2O (2) are described. Complex 1 crystallizes in the triclinic space group P 1 , with a=8.592(2), b=17.18(3), c=8.028(2) A, α=102.48(5), β=110.24(2), γ=89.43(5)°, and Z=2. Refinement gave final R and Rw values of 0.072 and 0.108, respectively, for 3147 observed reflections. Complex 2 crystallizes in the orthorhombic space group Pbca, with a=21.949(3), b=14.97(2), c=12.964(6) A, and z=8. Refinement gave final R and Rw values of 0.050 and 0.070, respectively, for 3220 observed reflections. In both complexes, the central copper atom is essentially five-coordinated with a weakly coordinated perchlorate anion or water molecule at the sixth axial position. The terdentate ligand dpa (2,2′-dipicolylamine) coordinates meridionally in the equatorial plane and the bidentate pic (picolinate anion) forms an axial chelate with an apical coordination through its carboxylate group. Intermolecular stackings are observed between the pyridine rings of adjacent complex molecules. The electronic absorption spectra of complexes 1 and 2 varied to a large extent in organic solvents with different coordinating abilities, that is, a solvatochromism was observed for these complexes. Whereas, for a similar five-coordinate complex [Cu(dpa)( l -phe)]ClO4, which has a facially coordinated dpa with an apical coordination of its pyridyl group, such a chromism was not observed. This spectral behavior will be discussed in relation to their complex geometries.

Synthesis, structure, and preliminary magnetic studies of unprecedented hexacopper(II) barrel clusters with spin ground state S= 3

The structure of a discrete hexacopper(II) barrel cluster and that of a coordination polymer formed by a related hexanuclear repeating unit have been determined. The CuII metals of the hexanuclear units are held together by eight chelating L-prolinato type ligands, which in turn provide the eight oxygen donors trapping a sodium ion in the center. The structure of the [Cu6Na] unit in the discrete system and in the infinite cluster-chain are essentially the same and both display intra-unit ferromagnetic superexchange. A preliminary magnetic study shows that, for both compounds, the copper centers within the [Cu6] unit are ferromagnetically coupled, yielding an S = 3 spin ground state.

A cyclic tetranuclear Ni2Gd2 complex bridged by amino acidato ligands, with an S = 9 ground state, derived from ferromagnetic spin-coupling between nickel(II) and gadolinium(III) ions

Synthesis and structure of a cyclic tetranuclear Ni(2)Gd(2) complex bridged by amino acidato ligands, with an S = 9 spin ground state, derived from ferromagnetic spin-coupling between S(Gd) = 7/2 and S(Ni) = 1 are reported.

Stabilities of five-coordinate ternary copper(II) complexes containing 2,2′-dipicolylamine and α-amino acids and X-ray crystal structure of [Cu(dpa)(l-phe)]ClO4 (dpa=2,2′-dipicolylamine, l-phe=l-phenylalaninate)

Abstract Stabilities of the five-coordinate ternary copper(II) complexes [Cu(dpa)(am)]+ containing 2,2′-dipicolylamine (dpa) and 11 different α-amino acid anions (am) have been studied by potentiometric and spectrophotometric titrations. The effect of the side chains of the amino acid ligand on stability is examined. The ternary complexes containing aromatic amino acids are significantly more stable than the complexes containing alkyl- and hydroxyalkyl-substituted amino acids, indicating the presence of a hydrophobic intramolecular interaction between the hydrophobic moiety of dpa and the aromatic side chains. The X-ray crystal structure of [Cu(dpa)( l -phe)]ClO4, where l -phe is l -phenylalaninate, is also described. The copper ion takes on a slightly distorted square pyramidal geometry with facially-coordinated dpa. There is no intramolecular ring-stacking between the pyridine ring of dpa and the phenyl ring of l -phe, whereas intermolecular stacking is observed between the pyridine rings of adjacent complex molecules.

Synthesis, structure, DNA-binding, and nuclease activity of a 3d–4f mixed metal nitrosyl complex, [Pr(phen)2(MeOH)(H2O)2][Fe(CN)5(NO)] · (Phen)(DMF)(MeOH)(H2O)

A cyano-bridged heterometallic lanthanide-transition metal nitrosyl complex, [Pr(phen)2(MeOH)(H2O)2][Fe(CN)5(NO)] · (Phen)(DMF)(MeOH)(H2O) (Phen = 1,10-phenanthroline and DMF = dimethylformamide), has been synthesized from reaction of PrCl3 · 6H2O with 1,10-phenanthroline in methanol and sodium nitroprusside followed by crystallization from DMF. The crystal structure shows that the complex is a 1-D chain, stabilized by coordination, hydrogen-bonding, and π–π stacking interactions. The complex shows nuclease activity with pUC19 supercoiled DNA in DMF/Tris-HCl buffer in the presence of H2O2.

Structure of the centred icosahedral samarium cluster formed by bis(l-prolinato)nickel(ii) ligands

The centred icosahedral twelve-coordinate samarium cluster formed by six bis(L-prolinato)nickel(II) ligands is synthesized and its crystal structure determined.

Solvent effects on acetylacetonato iron complexes

Abstract Interactions of various solvents with Fe(acac) 2+ , Fe(acac) 2 + and Fe(acac) 3 (the expression represents the solvated species: acac t- is the 2,4-pentanedionate ion, acetylacetonate ion) were investigated through observing v (FeO) and v (CO) in resonance Raman spectra. In the Fe(acac) 2+ system, both v (CO) and v (FeO) correlate with donor number ( DN ): the v (CO) band shifts toward high frequency with the increase in DN , while the v (FeO) band exhibits the inverse trend. The relation between v (CO) and v (FeO) in different solvents is a good example of the bond length variation rules (the donor-acceptor concept). In the Fe(acac)3 system, i.e. the non-direct solvation system, v (CO) shifts toward low frequency with increase in the relative dielectric constant (ϵ r ) of the solvent, whereas v (FeO) is constant, independent of ϵ r These facts indicate that the CO bond of the acacligand is lengthened by the polarizability effect of the solvents, while the FeO bond in the inside of the complex is not influenced. On the other hand, v (CO) and v (FeO) do not correlate with ϵ r in the Fe(acac) 2+ system. They indicate that the direct effect (donor effect) of the solvent molecules on the metal is larger than macroscopic effects such as polarizability. In the Fe(acac) 2 + system, the v (CO) shift exhibits a similar trend to that in Fe(acac)3, whereas the shift of v(FeO) is similar to that in Fe(acac) 2 + . The results suggest that Fe(acac) 2 + is influenced by both the macroscopic and direct effects of the solvents. To confirm this in the Fe(acac) 2 + system, solid samples were prepared by freeze drying the solutions and measuring their resonance Raman spectra.